The reptile undergoes rapid molecular evolution but is largely unchanged since the time of the dinosaurs.

Often called a living fossil, the tuatara reptile looks as if it has hardly changed in the more than 200 million years since it shared habitat with the early dinosaurs. But appearances can be deceiving. A report published in March in the journal Trends in Genetics revealed that the lizardlike native of New Zealand has undergone the fastest rate of molecular evolution of any vertebrate animal studied thus far.

Evolutionary biologist David Lambert of Griffith University in Australia and his team analyzed DNA samples taken from ancient tuatara bones and from living specimens. He found that over the past 9,000 years, parts of the tuatara genetic code have changed 50 percent more quickly than those of any other vertebrate tested by the same method. “Given this high rate of molecular evolution, the stable morphology of tuatara over tens of millions of years is remarkable,” the team writes in its report.

The finding shows that changes in the genetic code don’t always dictate changes in the appearance, function, or behavior of an organism. “Evolution is multidimensional,” Lambert says. “It’s not just about DNA.”